[0001] This invention relates to a fuel injector for supplying liquid fuel to an air inlet
duct of a spark ignition engine, the injector comprising a valve seat member on one
face of which is formed an annular seating element for engagement by a solenoid actuated
plate valve member, an orifice in the seat member through which fuel under pressure
can flow when the valve member is lifted from the seating element and a tubular outlet
through which in use fuel flows from the orifice to the air inlet duct.
[0002] Such injectors are well known in the art and the physical dimensions of the injector
have to meet a standard in order to allow interchangeability with injectors which
employ different types of valve member. As a result the distance between the orifice
and the end of the tubular outlet can be undesirably long when certain spray formations
are required. For example, if two sprays are required for use with an engine having
two air inlet ducts per cylinder, it is known to form two orifices which are angled
to achieve the desired divergence. The extent of divergence is however limited without
increasing the diameter of the tubular outlet, by the fact that the spray will impinge
upon the wall of the outlet. As an alternative it has been proposed to provide a target
at or near the end of the tubular outlet and to direct the fuel as a jet at the target.
The target should divide the jet and also break up the jet to form the desired two
diverging fuel sprays. In practice however it is found that the sprays are uneven
unless the injector is produced to a very high and undesirable, degree of accuracy.
[0003] With other injectors it is desired to produce a single bushy spray that is to say
a spray which has a large cone angle. The fact that the orifice is spaced from the
end of the tubular outlet limits the degree of spread of the spray and if a conical
target is used the same problem is encountered as described above namely that the
injector must be produced to a very high degree of accuracy in order to form an even
spray.
[0004] The object of the present invention is to provide an injector of the kind specified
in a simple and convenient form.
[0005] According to the invention in an injector of the kind specified the orifice is designed
to produce a spray within the tubular outlet and at its end remote from the orifice,
the outlet defines at least two diverging bores through which the spray passes to
form, in the case of an injector having two bores, two diverging sprays.
[0006] Examples of fuel injector in accordance with the invention will now be described
with reference to the accompanying drawings in which:-
Figure 1 is a sectional side elevation through the injector,
Figure 2 is a section to an enlarged scale of part of the injector seen in Figure
1,
Figure 3 is an inverted plan view of the part see in Figure 2,
Figures 4 and 5 show alternative shapes for the part.
Figure 6 is a side view of the outer insert member of a two part insert for incorporation
in the injector seen in Figure 1,
Figure 7 is a sectional side elevation of the outer insert member seen in Figure 6
taken on the line BB of Figure 10,
Figure 8 is an end view in the direction of the arrow A of Figure 6,
Figures 9 and 10 are opposite end views corresponding to Figures 6 and 7,
Figure 11 is a sectional side elevation of the inner insert member,
Figure 12 is an end view of the inner insert member.
Figure 13 is a sectional side elevation of a modified form of the outer insert member
with the section taken on the line YY of Figure 15.
Figures 14 and 15 are opposite end views of the outer insert member of Figure 13,
Figure 16 is a sectional view showing the outer insert members of Figures 13, 14 and
15 with an inner insert member assembled therein, and
Figure 17 is a sectional side elevation of a modified two part insert shown located
in an outlet member of the nozzle.
[0007] Referring to Figure 1 of the drawings the injector comprises a hollow generally cylindrical
outer body 11 formed from magnetic material and within which there extends a hollow
flanged core member 13 formed from magnetic material. Extending within the core is
a passage 14 which extends from an inlet 12 in the body.
[0008] Surrounding the core 13 is a former 16 which is formed from synthetic resin material
and upon which is wound a solenoid winding 17.
[0009] The body 11 defines an integral radially inwardly extending annular shoulder 18 against
which there is trapped by means of a non-magnetic valve seat member 21, an annulus
19. The seat member 21 is held in position by means of a tubular outlet member 15
which in use projects into the air inlet manifold of the engine. The seat member 21
is in the form of a disc the diameter of which is equal to the internal diameter of
the body 11 and the disc has a central orifice 22 formed therein. The orifice is surrounded
by an inner annular seat element 23 which is engageable by a plate valve member 24
biased by a spring 26 into contact with the seat element and located within the annulus
19. The plate valve member has a plurality of openings 25 and it is formed from magnetic
material so that when the winding 17 is energised the flange and core member assume
opposite magnetic polarity and the valve member is attracted away from the seating
element against the action of the spring. In this situation fuel can flow through
the passage 14 and the openings 25 to the central orifice 22. The movement of the
valve member towards the shoulder is limited by a non-magnetic shim (not shown).
[0010] Mounted within the outlet member 15 is a non-magnetic tubular outlet 40 having a
flange 41 at its end adjacent the seating member, the flange locating in a complementary
recess formed in the outlet member 15. The tubular outlet 40 defines a chamber 42
which is closed at its end remote from the seating member except for a pair of divergent
bores 43 which extend from the chamber 42. The bores 43 are constructed so that there
is defined at the junction thereof a sharp edge 44.
[0011] The orifice 22 can be regarded as being formed in a thin plate and it is designed
so that good atomisation of the fuel flowing therethrough is obtained while at the
same time it is relatively insensitive to variations in the temperature to which the
injector is subjected during use. When in use the valve member is lifted from the
seating fuel flows through the orifice to form a spray within the chamber 42 and as
the spray progresses along the chamber it becomes evenly distributed and exits through
the bores 43 to form two diverging sprays. In a particular application the angle between
the two bores 43 is chosen so that the resulting sprays are directed into a pair of
air inlet ducts of a cylinder of a spark ignition engine.
[0012] An important aspect of the invention is the provision of flats 45 on the outer side
of the tubular outlet 40 as shown in Figure 3. The flats communicate with a transverse
recess 46 formed in the end of the flange of the tubular outlet adjacent the seating
member. However, the transverse recess may be replaced by rectangular openings such
as are illustrated in Figure 13.
[0013] In use when the flow of current in the winding 17 ceases and the valve member returns
to the seating element, fuel spray which is already within the chamber 42 continues
to move along the chamber and through the bores 43. In so doing air is drawn into
the chamber along the flats 45 and the recess 46. In more conventional injectors of
this type the fuel spray tends to be halted when the valve member closes onto the
seating element and then tends to dribble from the injector outlet thereby resulting
in poor combustion of the fuel.
[0014] Figures 4 and 5 show alternative configurations for the chamber 42, the chamber in
the example of Figure 4 being tapered towards the bores 43 and that in Figure 5 having
a rounded end adjacent the bores 43.
[0015] If it is desired to produce a single bushy spray then three or more bores 43 can
be provided the bores being equiangularly disposed about the axis of the tubular outlet
40. It is convenient with this construction to provide the same number of flats 45
as there are bores.
[0016] In a modification (not shown) the flange 41 can be omitted and the tubular outlet
40 secured within the tubular outlet member 15 by reason of its being an interference
fit or by means of welding or adhesive. The tubular outlet 40 may be formed from a
plastics.
[0017] The tubular outlet 40 and the outlet member 15 could be formed as a single item with
the flats 45 defined by axial passages extending the length of the combined unit.
[0018] The tubular outlet 40 can be constructed as a two part insert both parts of which
are moulded from synthetic resin material. The insert comprises a hollow outer insert
member 47 seen in Figures 6 - 10, which in the example is of triangular section. At
its end remote from the seat member 21 the outer insert member has an integral end
wall in which there are formed three diverging bores 48 each of which defines an outlet
49. The bores are positioned at the apices of the outer insert member and the side
walls of the the outer insert member are formed with rectangular cutouts 50 which
extend to a level 51 from the end of the member adjacent the seat member 21. The remaining
portions of the insert member are hereinafter termed legs 52 and each leg at its free
end is provided on its outer surface, with an axial projection 53 having a rounded
outer peripheral surface. The projections locate against a step formed in the bore
in the outlet member 15.
[0019] Positioned within the portion of the outer insert member defined by the legs 52 is
an inner insert member 54 seen in Figures 11 and 12, which is of tubular form. The
end of the inner insert member adjacent the seat member 21 is provided with four outwardly
and axially extending projections 55 which when the inner and outer insert members
are assembled together locate against the ends of the legs 52. The fact that there
are three legs 52 and four projections 55 means that whatever the relative angular
position of the insert members there will always be adequate location.
[0020] The other end of the inner insert member is cut off at an angle so as to form a sharp
edge which defines a central opening 56. The bore 57 can be tapered as shown in solid
outline or it can be substantially uniform in diameter as shown in dotted outline
with a tapered section at the end leading to the central opening 56. In the former
case a jet of fuel will issue through the opening 56 and three jets of fuel will issue
through the openings 49. In the latter case the fuel leaving the opening 56 will be
in the form of a spray so that three sprays of fuel will issue through the openings
49.
[0021] The length of the inner insert member is such that the inner end thereof lies below
the level 51 but the length of the right cylindrical portion of the outer wall thereof
is such that the inner ends of the cutouts 50 form rectangular openings which communicate
with channels 58 (Figure 8) defined between the wall of the bore in the outlet member
15 and the flat faces of the outer insert member. The fuel which flows through the
opening 56 induces a flow of air along the channels, and through the rectangular openings.
The flow of air will entrain any droplets of fuel which may collect on the end of
the outer insert member surrounding the openings 49 and on the end of the outlet member
15 which as will be seen in Figure 1, is partly recessed.
[0022] An air flow is also induced through the inner portions of the channels 58 by the
flow of fuel through the orifice 22. The air flow taking place through openings to
the bore 57 from the channels through openings 59, being defined between the projections
55.
[0023] In an alternative arrangement the openings 59 are omitted by reason of the fact that
the projections 53 are flush with the end of the inner insert member. In this case
the inner insert member 54 is provided with three drillings (not shown) which extend
from the channels 58 respectively into the bore 57, the drillings being angled in
the direction of fuel flow.
[0024] Where the insert is designed to produce three sprays of fuel the end portion of the
outer insert member can be chamfered, the chamfer breaking into the bores 48, to provide
clearance for the sprays.
[0025] It will be understood that the outer insert member may be provided with two bores
48 therefore defining two outlets. In this case two channels only are defined between
the bore in the outlet member 15 and the outer insert member.
[0026] Turning now to Figures 13, 14 and 15 there is shown a modification to the outer insert
member 47A. In this case the cutouts 50 are eliminated and only the portion of the
insert member 47A which in the assembled nozzle is furthest from the seat member 21
is of triangular section the remaining portion of the insert member being of cylindrical
section with an annular rim 60.
[0027] Channels corresponding to the channels 58 are defined between the sides of the triangular
portion of the outer insert member 47A and the wall of the outlet member 15 and these
channels which extend only so far as the cylindrical portion of the insert member,
communicate with generally rectangular openings 61 which extend through the side walls
of the insert member. The openings 61 are located at substantially the same positions
as the inner ends of the cutouts 50 in the example shown in Figure 6 and air can pass
through the openings during the use of the nozzle. Figure 16 shows in section, the
outer insert member 47A with an inner insert member 54A located in position. The inner
insert member 54A corresponds to the inner insert member 54 except that the projections
55 are replaced by a continuous annular rim 62.
[0028] Figure 17 shows a modified form of the two part insert. The outer insert member 63
is secured by adhesive within the outlet member 15 as previously suggested, but in
addition, the inner insert member 64 is secured by adhesive or in any other convenient
manner, within the outer insert member. Figure 17 shows a two part insert which has
two outlets 6 and a pair of flats not shown, are provided on the external surface
of the outer insert member 63 to allow air flow into the bore in the inner insert
member. Both the insert members 63 and 64 are spaced from the seat member 21 to allow
the air flow.
1. A fuel injector for supplying liquid fuel to an air inlet duct of a spark ignition
engine comprising a valve seat member (21) on one face of which is formed an annular
seating element (23) for engagement by a solenoid actuated plate valve member (24),
an orifice (22) in the seat member through which fuel under pressure can flow when
the valve member (24) is lifted from the seating element (23), a tubular outlet (40)
through which in use, fuel flows from the orifice (22) to the air inlet duct, characterized
in that the orifice (22) is designed to produce a spray within the tubular outlet
(40) and at its end remote from the orifice (22) the tubular outlet (40) defines at
least two diverging bores (43) through which the spray passes to form in the case
of an injector having two bores (43), two diverging sprays.
2. A fuel injector according to Claim 1 characterized by means (45, 46, 58, 50, 61)
for admitting air into the tubular outlet (40) at a position removed from said diverging
bores (43).
3. A fuel injector according to Claim 2 characterized in that said means (45, 46)
comprises flats (45) formed on the exterior surface of the tubular outlet (40) and
transverse recesses (46) formed at the end of the tubular outlet (40) adjacent the
seat member (21), said recesses (46) communicating with said flats, the tubular outlet
(40) being mounted within a tubular outlet member (15), the flats (45) forming with
the internal surface of the tubular outlet member (15), channels through which air
can flow from the air inlet duct.
4. A fuel injector according to Claim 1 characterized by openings in the tubular outlet
(40) and means communicating said openings with the end of the injector which in use
is disposed in the air inlet duct.
5. A fuel injector according to Claim 1 characterized in that said tubular outlet
(40) is formed by an outer insert member (47, 47A, 63) and an inner insert member
(54, 54A, 64) which is located within the outer insert member, said outer insert member
defining the diverging bores (48) and the inner insert member defining a bore (57)
which receives the fuel spray from the orifice (22) and has an outlet (56) which directs
the fuel spray to the entrances of said diverging bores (48).
6. A fuel injector according to Claim 5 characterized in that the wall of said outer
insert member (47) is formed with slots (50) extending from the end thereof adjacent
the seat member (21) said slots (50) being closed over substantially the whole of
their length by the inner insert member (54) so as to form openings through which
air can enter into the space defined between the outlet (56) defined by the inner
insert member (54) and the entrances to said diverging bores (48).
7. A fuel injector according to Claim 6 characterized in that said inner insert member
(54) is provided with channels (59) at its end adjacent the seat member (21) whereby
further air can be admitted into the bore (57) in the inner insert member adjacent
the orifice (22).
8. A fuel injector according to Claim 7 characterized in that said openings and said
channels (59) communicate with channels (58) defined between the outer surface of
the outer insert member (47) and the inner surface of a tubular outlet member (15)
in which the inner and outer insert members (47, 54) are located.
9. A fuel injector according to Claim 5 characterized in that the outer insert member
(47A) defines a plurality of openings (61) in its wall, said openings (61) being positioned
to allow a flow of air into the space defined between the outlet (56) defined by the
inner insert member (54) and the entrances to said diverging bores (48).
10. A fuel injector according to Claim 5 characterized in that said inner insert member
(54, 54A) is provided with a series of projections (55) or a peripheral flange (62)
at its end adjacent the seat member (21) said outer insert member (47, 47A) being
shaped to locate said projections or flange, and the outer insert member (47, 47A)
defining projections (53) or a flange by which it is secured within a tubular outlet
member (15).
11. A fuel injector according to Claim 5 characterized in that the inner insert member
(64) is secured within the outer insert member (63) and the outer insert member (63)
is secured within a tubular outlet member (15).